Modulating microbial communities for human health requires understanding the response of communities to invaders, but little is known about the mechanistic bases for community invasion. Our goal is to determine the genetic basis for invasion in the simple model, the gut community of Manduca sexta, and determine the impact of invasion on the meta-metabolome of the host-community complex. We will identify genes involved in invasion and then determine their role in competition and cooperation in the community and their impact on the metabolome to generate hypotheses about the role of signal molecules, antibiotics, and nutrients in community interactions. The project's innovation derives from the marriage of systems-level analysis of metabolite profiles with reductionist genetic analysis, the application of genetics to community-level phenotypes, quantification of microbial populations with luminescence imaging in live animals, and cutting edge chemical technology. The work has the potential to advance the field of microbial community ecology by providing a basis for deriving models about community behavior in the face of perturbation that may apply directly to human health.